Anisotropy of the spectroscopy properties of the wurtz-stannite Cu2ZnGeS4 single crystals

In this study, the near band edge anisotropic optical properties of wurtz-stannite (WS) Cu2ZnGeS4 single crystals were characterized using polarization-dependent transmittance and electrolyte electroreflectance (EER) techniques. Single crystals of Cu2ZnGeS4 were grown by chemical vapor transport method using iodine as a transport agent. Analysis of absorption spectra revealed indirect allowed transitions for Cu2ZnGeS4 with the band gaps of 2.02 (2.07) and 2.08 (2.14) eV for E‖b and Е‖a polarization configurations at 300 (10) K. The room-temperature EER spectra in the vicinity of the direct band edge showed anisotropic transitions at around 2.38, 2.44 and 2.45 eV for E‖b, Е‖a and Е‖c polarizations, respectively. Based on the experimental observations and recent band-structure calculations a plausible band diagram near band edge of WS-Cu2ZnGeS4 was constructed.

► Analysis of absorption spectra revealed indirect allowed transitions for Cu2ZnGeS4.
► Polarization-dependent EER measurements of Cu2ZnGeS4 were performed at 300 K.
► Cu2ZnGeS4 exhibits E1, E2 and E3 anisotropic transitions for E‖b, E‖a, and Е‖c.
► A plausible band diagram at the near band edge of Cu2ZnGeS4 was constructed.